The increasing service life of telecommunication satellites and the changing requirements related to different missions have resulted in the development of new generations of satellites intended to improve mission flexibility. This is notably the case for telecommunications antennas and the mechanisms related thereto, for which designers aim for example to provide the option of choosing between several coverage zones and several frequency planes, and thus to give the option of changing satellite missions once they are in orbit.
There are several approaches to improving the mission flexibility of telecommunications satellite antennas. A first approach uses an active antenna known as a computational beamforming antenna. To improve mission flexibility, these antennas make it possible to target an extended geographical area by moving the beam. However, these antennas require a complex and costly electronic module. Indeed, this electronic module requires for example the integration of numerous processors to determine the orientation of the beam, radiating elements to form the beam, energy supply equipment to power the processors and high-performance heat-dissipation equipment. Inclusion of all of these elements significantly increases the cost of designing and launching a satellite fitted therewith into space.
A second approach uses a device for switching between several sub-reflectors mounted on a shaft. Rotating this shaft in relation to the frame of the antenna structure, to which a main reflector and a feed are rigidly connected, makes it possible to target several coverage zones on the Earth.
In a known implementation, the axis of rotation of the shaft bearing the sub-reflectors is contained within a plane, commonly referred to as a focal plane, including the centre of the main reflector, the centre of the sub-reflector and the feed. So as not to interfere with the field scanned by the wave beam of the antenna, the shaft bearing the sub-reflectors needs to be connected to the frame of the mechanical structure from behind the antenna, creating a large cantilever. This support from the rear requires a mechanical structure that is very inflexible, voluminous and heavy to enable it to withstand the stresses applied to the satellite platform during launch from a spacecraft.
More generally, the issue of stowing, enabling all of the equipment to be kept in place during a launch phase, and unstowing, enabling the equipment to be released and made operational, is key. The solutions currently available for switching between several reflectors do not address this issue efficiently.